Darwin’s finches: A beak for every occasion

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What a strange, long trip it has been for Darwin’s Finch! At some point in its natural history, it abandoned the comfort of the mainland (though some theories link the common ancestor of finches to the Caribbean) and reached this mostly barren, inhospitable archipelago in the middle of the Pacific Ocean. The journey was far from over.

Upon arrival, the environment would turn this species into one of the most versatile examples of evolution on our planet. It’s as if before traveling to the Galápagos, these birds had packed their bags at a molecular level, accessing the matrix of their very DNA, playing with the inner circuits and creating a magical chip with which they could change their beaks according to what they found upon arrival on the islands.

Of course, it is far more complex than this. But the finches’ beaks are obviously different from one another. Obviously? Well, in retrospect, yes, but even as keen an observer as Charles Darwin didn’t discern that he was looking at the same species on the different islands he visited. It was only later, with the help of other scientists, that the finches’ remarkable variety became part of his theories on the transmutation of species.

This species is considered one of the most versatile examples of evolution on our planet.

Some beaks were as thick as the head of the bird, while others were thin, and then there was the beak of the Vegetarian Finch, which seemed carved at will by a rudimentary sculptor. Scientists soon equated these beaks to what each species ate, finding that each beak was “adapted” to a specific food source. For some, ideal for crushing seeds, others for picking at fruits and flowers or snatching up insects, and one of them, the Woodpecker Finch, didn’t always use its beak directly, but inserted thorns and small twigs into crevices of tree branches and trunks to extract larvae.

An evolutionary journey

The adaptability of these species is mind- blowing. On the remote island of Wolf (a small islet located in the extreme northwest of the archipelago), the only finch that inhabits the place feeds not only on seeds and insects, but most remarkably, on the blood of sea lions and iguanas, puncturing their necks with its pointed beak, or pecking at the base of Nazca boobies’ wing feathers.

According to the most recent classification systems, the genus to which the Darwin’s finches belong includes up to 17 species. They are one of the great examples of what is known as “adaptive radiation”, a process by which, through evident isolation between communities of a common species, new species “radiate”, diverging at a genetic level. The fascinating thing is that not all the finches are isolated today, and it is common to find several species in a single tree…

Darwin’s Finches have a Swiss-army knife for a beak.

It is also fascinating to note that the differentiator between species is not always easy to distinguish. The Medium Ground-Finch, for example, reveals beaks of different sizes and these differences don’t mean that they are separate species. Science, of course, is always more than meets the eye.

But what is perhaps most fascinating is that these species not only evolved hundreds of thousands of years ago, but, according to certain studies, are doing so now, at this very moment, on at least one of the islands. This evolutionary process, if confirmed, would have to be considered the fastest evolutionary process of all vertebrates: an incomparable window onto how evolution works in all animals.

They may look tiny and inconspicuous in the field, but the uniqueness of these birds makes them giants in the eyes of Science. Such is the complexity of the finch’s evolution that less than a decade ago ornithologists spoke of only 13 species; today, thanks to DNA studies, we’re at 17… and counting.

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